The present invention relates to ultrasounds systems and more particularly to control of probe heating in such systems.
Ultrasound is an increasingly used tool for noninvasively examining the human body. Diagnostic ultrasound is routinely used to examine a beating heart, diagnose valve abnormalities, monitor fetal growth, and detect lesions in the liver. Furthermore, ultrasound is commonly used to diagnose regions of atherosclerosis by measuring blood flow.
A typical ultrasound system works by transmitting high frequency acoustic signals into the body using a piezoelectric transducer. The ultrasound transducer converts electrical energy into mechanical energy (ultrasonic wave) that propagates into the body. The ultrasonic wave propagates in the body and is scattered, absorbed and reflected by various tissues. The ultrasound echo that is directed back to the piezoelectric transducer is converted from mechanical energy back to electrical energy. The ultrasound echo strength is detected and is typically used to modify the intensity of pixels in a digital display screen to create an image of the tissue in the body.
Ultrasound transducers typically include the following materials: backing, PZT, matching layers and a lens. In some system modes, the transmit voltage to the PZT is decreased because of the power dissipation within the ultrasonic transducer. The power is dissipated in the various transducer materials depending on the loss mechanism. The absorbed power causes heating of the probe that may be unacceptable to patient comfort or material thermal tolerances. Other designs may also convert the electrical to mechanical energy such as capacitive membrane ultrasonic transducers. These transducers also experience thermal limitations.
Ideally, the majority of power to a transducer dissipates in the human body and not the various transducer materials during transmit. The human body actually acts as a xe2x80x9cheat sinkxe2x80x9d pulling transmit power away from the transducer. Of course, some of the power from the transducer is reflected and scattered back towards the transducer allowing images to be formed. Unfortunately, when the transducer is not transmitting into the body, some of the power is dissipated in the transducer materials causing probe heating. This transducer heating restricts the amount of transmit voltage during imaging. Therefore, the transducer loses transmit sensitivity because the system does not detect when the transducer is coupling into human soft tissue or air. Accordingly, what is needed is a system and method for overcoming the above-identified problems. The method and system should be cost-effective, compatible with existing systems and easily implemented on such systems. The present invention addresses such a need.
A method and system for controlling probe heating in an ultrasound system is disclosed. The method and system comprises electrically exciting a transducer within the probe; and detecting at least one pulse characteristic from the excited transducer. The method and system further includes analyzing at least one pulse characteristic to determine if the probe is coupling into a reflecting medium such as air or into tissue.
Accordingly, a system and method in accordance with the present invention detects when an ultrasound transducer is coupling energy into a patient or into a reflecting medium such as air. In so doing, the thermal performance of the transducer improves by allowing an increase in the duration and level of the transducer excitation voltage.